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<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/>

<a NAME="E1:7"/><i><font color="Green">E18</font></i>: 
( <font color="Maroon">X</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">X</font> &amp;  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">X</font> <a href="hidden.html#R1">=</a> <font color="Maroon">H<sub>1</sub></font>( <a href="lattice3.html#K1" target="_self">BooleLatt</a> <font color="Maroon">X</font>) )
 
<b>by </b><i>, <a class="ref" href="zfmisc_1.html#D1">ZFMISC_1:def 1</a></i>;<br/>
<b>then reconsider </b><font color="Maroon">x</font> = <font color="Maroon">X</font> as   <a href="struct_0.html#NM1">Element</a> of <span class="p1">(<span class="default"><a href="lattice3.html#K1" target="_self">BooleLatt</a> <font color="Maroon">X</font></span>)</span> ;<br/>
<div><i><font color="Green">E22</font></i>: <a class="txt" onclick="hs2(this)" href="javascript:()" title="7_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">y</font> be   <a href="struct_0.html#NM1">Element</a> of <span class="p1">(<span class="default"><a href="lattice3.html#K1" target="_self">BooleLatt</a> <font color="Maroon">X</font></span>)</span>;<br/><b>thus </b><font color="Maroon">x</font> <a href="lattices.html#K3">"\/"</a> <font color="Maroon">y</font> = 
<font color="Maroon">x</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">y</font>
<b>by </b><i/>
<br/>.= 
<font color="Maroon">x</font>
<b>by </b><i>, <a class="ref" href="xboole_1.html#T12">XBOOLE_1:12</a></i>
;<br/><b>hence </b><a NAME="E2:7_1"/>
<font color="Maroon">y</font> <a href="lattices.html#K3">"\/"</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font>
 ;<br/></div><b>end;</b></div>
<b>thus </b><a NAME="E4:7"/>
 <a href="lattice3.html#K1" target="_self">BooleLatt</a> <font color="Maroon">X</font> is <a href="lattices.html#V14">upper-bounded</a>
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="7_2"><b>proof </b></a><div class="add">

<b>take </b>
<font color="Maroon">x</font>
; <i><font color="Red">:: according to </font></i><a class="ref" href="lattices.html#D14">LATTICES:def 14</a><br/>

<b>thus </b><a NAME="E1:7_2"/>
for <font color="Olive">b<sub>1</sub></font> being   <a href="subset_1.html#M1">Element</a> of the <a href="struct_0.html#U1">carrier</a> of <span class="p1">(<span class="default"><a href="lattice3.html#K1" target="_self">BooleLatt</a> <font color="Maroon">X</font></span>)</span> holds <br/> ( <font color="Maroon">x</font> <a href="lattices.html#K1">"\/"</a> <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font> &amp; <font color="Olive">b<sub>1</sub></font> <a href="lattices.html#K1">"\/"</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font> )
 <b>by </b><i/>;<br/>


</div><b>end;</b></div>

<b>hence </b><a NAME="E5:7"/>
 <a href="lattices.html#K6">Top</a> <span class="p1">(<span class="default"><a href="lattice3.html#K1" target="_self">BooleLatt</a> <font color="Maroon">X</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">X</font>
 <b>by </b><i>, <a class="ref" href="lattices.html#D17">LATTICES:def 17</a></i>;<br/>


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